The chromium-catalyzed synthesis of 1-hexene from ethylene constitutes a commercially significant process for the selective preparation of this alpha olefin, which in turn is useful for preparing a range of polyolefins when deployed as a comonomer with ethylene. A widely reported chromium catalyst system comprises chromium(III) carboxylates (e.g. tris(2-ethylhexanoate) chromium(III) (Cr(EH)3), a pyrrole-containing compound, and a metal alkyl for the selective production of 1-hexene.
Many oligomerization catalyst systems contain a chromium-containing compound, a pyrrole or pyrrole-containing compound, at least one metal alkyl, optionally a solvent, and optionally additional components, which can be combined in various ways and in various ratios to afford the catalyst system. Some catalyst system preparative methods appear to rely on the presence of particular solvent to aid in the activation of the catalyst components, while other methods may rely on using an excess of a metal alkyl or other activator. Typically, any method of preparing, activating, and using a catalyst system may present challenges with respect to its particular preparation, activation, and stability, as well as to the activity and selectivity provided by the catalyst system.
Therefore, it would be useful to discover and develop new oligomerization catalyst systems, new methods for preparing the oligomerization catalyst systems, and new methods for using the oligomerization catalyst systems for preparing an oligomerization product that might provide greater efficiency and cost effectiveness. In one aspect, new oligomerization catalyst systems and methods for preparing the oligomerization catalyst systems are needed that might afford greater activity and more efficiency, and possibly lower the cost or increase the efficiency of using the chromium-based catalyst system.